In order to prevent a thermistor of a temperature sensor from indicating a resistance value that is deviating from the value it should have at a certain temperature, in particular in a high temperature zone, the atmosphere around thermistor has to be kept consistent. A prior art as disclosed by Japanese Patent Laid-Open No. 6-307943 teaches to provide a heat resisting cap housing a thermistor with an air ventilation hole.
However, if the ventilation hole is clogged by some reason, it fails to maintain the ambient of a thermistor consistent. The problem that resistance of a thermistor deviates much from a should-be value still remains unsolved.